when(backingMap.remove(KEY, current)).thenReturn(false);

    assertEquals(countToRemove, multiset.remove(KEY, countToRemove));
    assertEquals(0, current.get());
  }

  public void testRemoveExactly() {
    ConcurrentHashMultiset<String> cms = ConcurrentHashMultiset.create();
    cms.add("a", 2);
    cms.add("b", 3);

    assertThrows(IllegalArgumentException.class, () -> cms.removeExactly("a", -2));